RectangleTexture - prevent rounded corners from skewing with aspect ratio

[mariomatasystems]

I notice if the RectangleTexture is not 1:1 the rounded corners skew,

It would be more useful to keep the rounded corners consistent

Might be wrong (chatgpt) but i think we can tweak the frag code to account for the aspect.

changing this

float roundn=roundness*min(size.x,size.y);

to this

vec2 aspectScale = vec2(1.0, size.y / size.x);
float roundn = roundness * length(size * aspectScale);

[pandrr]

thanks, good input!

[pandrr]

created issue: #909